Magnetic sound system



Nov. 10, 1953 A. c. ALBEE ETAL 2,658,951

MAGNETIC SOUND SYSTEM Filed 001:. 50, 1948 3 Sheets-Sheet 1 Z [/VVEJVYWRS I Y HRTHLLR E. HLBEIL HuEH C. RI]

Nov. 10, 1953 A. C.-ALBEE ET AL 2,658,951

MAGNETIC SOUND SYSTEM Filed Oct. 30,' 1948 I 3 Sheets-Sheet 2 11V VE/V ZWRS HRTHun E. HLEEE Q Hun [L 111mm:

ATTORNEY NOV. 10, 1953 c, ALBEE ET AL 2,658,951

MAGNETIC SOUND SYSTEM Filed Oct. so, 1948 s Sheets-Sheet 3 8; Hum; .lllFmn BY F1 9 Patented Nov. 10, 1953 MAGNETIC SOUND SYSTEM Arthur G. Albee, Hollywood, and Hugh 0. Ward, Los Angeles, Calif., assignors to Radio Corporation of America, a corporation of Delaware Application October 30, 1948, Serial No. 57,434

6 Claims. (01. rap-100.2)

This invention relates to sound recording and reproduction, and particularly to a combination photographic and magnetic sound system and a magnetic recording and reproducin system.

Magnetic sound recording has several advantages over photographic recording in the production of motion pictures, such as immediate playback and the ability to erase the record on the recording medium and use it over again. In the transposition from photographic sound recording to magnetic sound recording, many features of photographic sound recording equipment may be used. For instance, since the sound is recorded on traveling record mediums of similar form, such as a tape or film with sprocket hole perforations, it has been found that the photographic mechanisms for obtaining a constant speed of the film past the'recording point may be utilized to good advantage. Much time and effort have been spent in obtaining a constant speed of advancement of a photographic sound medium past a sound recording or reproducing point, and such fihn drives are readily applicable for advancing a magnetic record medium. Furthermore, it is desirable that the same recorder be usable for both photographic and magnetic recording.

In general, it may be said that in their effort to meet the demand by motion picture producers for a synchronous sound reproducing mechanism employing magnetic film, engineers have been content to apply known principles to existing facilities which in general consisted of adding magnetic beads to standard optical motions.

The object was to reduce film fiutter as much as possible in apparatus of that kind without regard to the size and weight of the mechanism.

The consequent result was that the recording flutter.

The present invention is directed to a photographic recorder which permits recording a photographic record or a magnetic record using the same driving mechanism and film path, and, in addition, permits reproduction or erasing of the magnetic record so recorded, or any other magnetic record. The invention has also been embodied in a recorder for and reproducer of magnetic records alone, this new unit embodying some of the features of a photographic recording system. v

The principal object of the invention, therefore, is to facilitate the recording of either photographic or magnetic sound records.

Another object of the invention is to provide improved photographic and magnetic recorders and reproducers.

A further object of the invention is to provide a recorder for photographic sound records and a recorder and reproducer of magnetic sound records in which the improved features of photographic recording are utilized for the advance ment of both record mediums.

A still further object of the invention is to provide an improved magnetic recorder and reproducer adaptable for use in the usual processes of motion picture production.

With the foregoing objects in mind, my invention comprises a simple, compact magnetic recorder and reproducer in which film flutter is reduced to a minimum by mounting the head assembly in position to contact a reach of the film extending between an inertia controlled drum and a roller at points furthest removed from the points causing flutter disturbances. My invention also comprises the providing of tension rollers associated with a dashpot arrangement in close proximity to the inertia controlled flywheel.

Although the novel features which are believed to be characteristic of "this invention will be pointed out with particularity in the appended claims, the manner of its organization and the mode of its operation will be better understood by referring to the following description, read in conjunction with the accompanying drawings, forming apart hereof, in which:

Fig. 1 is an elevational view of the essential elements of a combination .photographic and magnetic recorder embodying the invention.

Fig. 2 is an enlarged, detailed view showing the positioning of the magnetic recording and reproducing headsof the invention.

Fig. 3 is a plan view of the recording head and reproducing head mount taken along the line 33 of Fig. 2.

Fig. 4 is a detailed view of the positioning mechanism for the recording and reproducing head.

Fig. 5 is a detailed view of the orientation mechanism for the recording and reproducing heads.

Fig. 6 is an elevational view of a magnetic recorder and reproducer.

Fig. '7 is a plan view of the recording and reproducing heads, and

Fig. 8 is an enlarged, detailed view of the shielding mount for the recording and reproduc ing heads.

Referring now to the drawings, in which the 3 same numerals identify like elements, a housing 5 has mounted, on the top thereof, a record medium magazine 6, the record medium 8, either photographic or magnetic, passing from the magazine to the left side of a sprocket 9 and held thereon by a pad roller mechanism 1 l. The typ of magnetic record is in the form of film or tape of the same size and having the same perforations as a standard "photographic film, "cit-her thirty-five millimeter or sixteen millimeter.

Thus, either a photographic or magnetic record 7 medium will be advanced through the recorder,

if both are of the same size.

. As shown by the arrows, the film Spassesirom bilizer mounted on the shaft thereof, around 'a fixed guide roller 15, around a film tensioning and :guide roller [-3, and back "to 'the'iright .side of sprocket 8, where it is held thereon by :a pad roller mechanism Hi. The film is then taken up :inthemagazine 6. The tension trollers l'fi and 16 are mounted on arms 20 and 21., respectively, which are pivoted at 22 and 23. The arms 20 and H are interconnectedby a coil spring 25, while the arm 21 extends' beyond the roller :16 and has connected thereto a piston rod 26 opereating in a dash pot 27!. Springs 28 and 2-9 hold the :pad rollers 11 and l'8, respectively, in position on the sprocket *9'. Theramount of tension introduced in the film loops between the sprocket 8 and the drum l4 and roller 15, .is' such that the necessary contact *pressureivis obtained between themagneti'c heads and the film, and alsofunctions with 'the'fiywheel .ontheshaft of drum "l4 and :dashpot 21 to filter out both low and high frequency speed variations. 7

What is desiredina mechanism of this kind is a resonatefrequency at the point where the sound recording and reproducing head contacts the filmwhich is substantially below the frequency of any disturbance; 'By the use of the inertia controlled drum M, and roller I5, of less inertia, a mechanical filter "is provided, and the series arrangement of the drum and roller insures a progressively lower resonate frequency in thetfilm as it'passes around themthan the frequency of the some, :such as the sprocket, causing the disturbances.

An electrical analogue of the system are two inductive filters in series with. the samecurrent 'both, wherein the variations in the cur rent is averaged .01 smoothed out in series.

It .is impracticable; however, to devise a mechanical filter system which will eliminate all vibrations in a device of this kind. Hence, viscons dampening, analogous to resistance in an electrical circuit, is incorporated in the system by providing a dashpot in close proximity to the drum to flatten the resonate peak frequencies. Such dashpot, therefore, contributes in the elimination of film flutter caused by the sprocket and minimizes the effect of film compliance as a dampening factor.

In Fig. 1, there is also shown a portion of an optical unit 30 which projectsa lightbeam onto the film 8 and which may be of the .type disclosed incop'ending application, Ser. No. 743,620, filed April 24, 1947. When a photographic film is advanced through the recorder, .a modulated light beam will be impressed on the film in the manner of normal photographic recording. For this 4 type of recording, the film path is as shown in Fig. 1.

Referring now to Figs. 1 to 5, inclusive, Fig. 2 showing the film path for a magnetic record, two brackets 34 and 35 are pivotally mounted on shafts 36 and 31, respectively, the other ends of the brackets supporting a recording head 40 and a reproducing head 4|. (See Fig. 3.) The arm 35 has, at its movable end, a drilled boss 42 in which is a rod 43 having a finger knob 41 and a fixed washer 48, between which and a shoulder of boss 42 is-a spring 43. (See Fig. 4.) That is, the rod 43 may be moved axially against the tension of spring 49 to remove the rod end 5| from a hole 50 in the back wall 52 of the housing compartment. The boss also has an extension 53 in which sis-a pin '44, the pin 44 being between the ends of a yoke 54 on the end of arm 35. Thus, when end5l is removed from the hole, the arms 34 and 35 may be simultaneously rotated on pivots 36 and 31, one position :being :asshown in Fig52, whereby the heads are in contact with a magnetic :film .58, and the other position-being shown in Fig. 1, whereby the heads are out of contact with the record medium, the :end of rod '43 then being in a slot '51.

Mounted adjacent the ends of arms 34 and 35 are the heads 40 and-4 I, these heads'a's shown in Fig. 5,;being mounted on plates 55 and 56 by means of a tap screw, such asshown at 58. The plates :55 and 56 are pinned to therespective arms by pins such as shown at ES, '50 thateach head may be rotated on .a substantially vertical axis to position the gaps BI "and '62 perpendicularly to the direction of 1110131011015 the film. To accomplish this adjustment, a tensioning spring 63 is positioned between one end of the plates and the respective arms, while the other ends of the. plates are moved towardand away 1mm the arms by means ofscrews, such as shown vatzfil. That is, by advancing the. screw $4, the head is rotated in one direction, and backing the screw off will permit the spring to rotate the head in the other direction.

' To position the heads 40 and '41 attheir proper positions transversely of the film, the screws 86 may be loosened and the respective nuts 6'! turned to either :force the 'arms 34 and 35 in one directicn against the tension :of springs. or permit the springs to move the :arms and .heads in the opposite direction. Thus, all necessary adjustments "may be easily made to position the gaps -.l and :62 in the correct position with respectto the =film. Asmentioned above, thehead 40 is :a recordshead, nnd'the'ihead 41 is a IBPID'. ducing head. "To accomplish erasing, a head 59 is provided which may be positionedas shown in full .lines in Fig. .1 during photographic recording, and to the dotted line position 14 in contact with the film 8 during magnetic record'- ing. Erasing energy is supplied to the erasing head when it is desired to erase any portion of the magnetic sound record. This unit, therefore, will record a photographic record, record a magnetic record, reproduce a magnetic record, or erase .a magnetic record, and is well adapted to zmotion picture production where eithertype of record may beneeded ata particular time.

Referring now to Figs. 6, 7, and 8, an all-magnetic recorder is shown, in which a base 710 carries a housing having a central compartment '1 l., a left-hand compartment 12, and a right-hand compartment 13. On top of the housing .is a magazine 15 similar to the magazine 5 in .Fig. l. A magnetic tape I6, which may be either thirtyfive or sixteen millimeter with sprocket tooth perforations, passes from the magazine over the left-hand side of a sprocket 18, under pad rollers I9, around a film tensioning roller 80, a drum 8|, which may have a flywheel mounted on the shaft thereof,-a film tensioning roller 82, to the right-hand side of sprocket 18, under pad rollers 89, and back to the magazine 15. The roller 80 is mounted on an arm 85 to which is attached a spring 86 for tensioning the film. The arm 85 is pivoted at 81 and has connected thereto anotherarm 88, at the end of which is a piston rod of a damping dashpot 90. The roller 82 is mounted on an arm 9|, which is pivoted at 92. An extension of the arm 9| is connected to a spring 93. Thus, the tensioning system for this form of film drive eliminates one of the tensioning rollers, such as I6, in the combination photographic and magnetic film drive, since roller 82 functions under tension instead of being fixed as in Fig. 1.

In contact with the portion of the magnetic film between drum BI and roller 82 is a recording head 94 and a reproducing head 95, these heads being mounted for rotational adjustment, similarly to the heads 40 and 4| in the first modification of the recorder. However, in this allmagnetic recorder, the heads are in a shielding mount 91, which has been milled to closely conform to the outside form of the heads, has a front plate 99 attached to the shield 91 by screws, such as shown at IN, and a cover I02, hinged at I03, and held closed under tension of a spring I 04. As shown in Fig. 8, the magnetic film 16 passes from the drum 8I to the gap I06 through an opening I01 between the upper tapered end of the shield 91 and the cover I02. The film then passes to the gap I08 of the head 95 and then to the roller 82 through an opening H formed between the right-hand edge of the mounting and the cover I02. This shield prevents interference of stray magnetic fields from the motor or other electrical elements from affecting the heads.

In the left-hand compartment 12 of the housing, is an oscillator-amplifier combination H2 provided with a meter II3, a bias potentiometer control H4, and a switch for making connections for the bias current for recording and for switching the input and output of the amplifier during recording and reproduction. The right-hand compartment contains the motor, the on and off motor switch I 20, and a counter I 2| with its resetting wheel I22.

This all-magnetic recorder provides a film motion comparable to high quality photographic film recorders and reproducers, it may be easily operated by operators familiar with photographic recorders and reproducers, and it will both record and reproduce magnetic records. If desired to use an erase head in this unit, it may be provided in the same manner as shown in Fig. 1 of the combination photographic and magnetic unit.

We claim:

1. A magnetic sound recorder and reproducing mechanism, comprising a sprocket, a speed stabilizing drum, a guide roller, said magnetic record medium passing over said sprocket around said drum, over said guide roller, and to said sprocket, tensioning and damping means contacting the portions of said magnetic record medium between said sprocket and said drum and guide roller, said tensioning means tensioning the portion of said magnetic record medium between 6, said drum and guide roller, magnetic recording and reproducing heads in contact with said record medium between said drum and said guide roller. means for adjusting said heads with respect to said record, and a shield surrounding said heads, said shield having a hinged cover with openings at the ends thereof to permit passage of said record to and from said heads.

2. A magnetic sound recorder and reproducer drive mechanism comprising sprocket means for advancing film into a loop, a pair of film-pulled rollers in said loop around which said film is: advanced by said sprocket means, means for tensioning and damping the portions of said film between said sprocket means and said rollers, said means also applying tension to said film between said rollers, magnetic recording and reproducing heads positioned against said film between and adjacent said rollers, and means connected to at least one of said rollers for stabilizing the rotation of said roller and the motion of said film between said rollers.

3. A magnetic recorder-reproducer of the drum roller film-driven filter system type comprising a sprocket for advancing a magnetic record medium through the mechanism, a spaced inertia controlled drum and a roller for guiding said medium in substantially a straight path, means positioned between said drum-roller guide and said sprocket for tensioning and damping said record medium, magnetic heads positioned between said drum and roller for contacting said record medium to record sound signals thereon and to reproduce sound therefrom, and means for adjusting said heads with respect to said medium.

4.. A sound film apparatus in accordance with claim 3, in which the tension rollers are mounted on pivoted arms and the said arms are resiliently connected together.

5. A sound film apparatus comprising a sprocket adapted to advance a film thereover, film driven inertia controlled drum and roller disposed in spaced relation to each other and around which the film is adapted to advance, tension rollers pivotally mounted between said sprocket and said drums and adapted to contact the approach and retreat sides of said film to take up slack therein, a shock arresting device associated with at least one of said rollers, means incorporated in said apparatus for dampening oscillations of said drum when a, film is passing therearound, and a magnetic sound recording and reproducing head disposed in position to contact the reach of a film between said drum and roller.

6. Sound film apparatus comprising a mounting plate, sprocket means mounted on said plate and adapted to advance a film thereover, an inertia controlled impedance drum and roller mounted on said plate in spaced relation to each other and around both of which said film is adapted to advance, stabilizing means for said drum, tensioning rollers pivotally mounted on said plate between said sprocket means and said drum, means for actuating said tensioning rollers to take up slack in said film and tension said film between said drums, means for damping movement of said tension rollers, and a magnetic sound head mounted on said plate in position to contact the reach of said film between said drum and roller.

ARTHUR C. ALBEE. HUGH C. WARD.

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